Question

what is a group of older stars that cluster together in a spherical shape and can contain up to one million stars per cluster called?
a globular cluster
open clusters
spherical clusters
accretion

Explanation:

Globular clusters are spherical - shaped groups of older stars that can have up to a million stars per cluster. Open clusters are more loosely - packed and usually contain younger stars. The term "spherical clusters" is not a standard astronomical term for this specific type of star cluster. Accretion refers to the process of growth by accumulation of matter, not a type of star cluster.

Answer:

a globular cluster